!function(win, lib) {
      var timer,
      doc     = win.document,
      docElem = doc.documentElement,

      vpMeta   = doc.querySelector('meta[name="viewport"]'),
      flexMeta = doc.querySelector('meta[name="flexible"]'),

      dpr   = 0,
      scale = 0,

      flexible = lib.flexible || (lib.flexible = {});

  // 设置了 viewport meta
  if (vpMeta) {

      console.warn("将根据已有的meta标签来设置缩放比例");
      var initial = vpMeta.getAttribute("content").match(/initial\-scale=([\d\.]+)/);

      if (initial) {
          scale = parseFloat(initial[1]); // 已设置的 initialScale
          dpr = parseInt(1 / scale);      // 设备像素比 devicePixelRatio
      }

  }
  // 设置了 flexible Meta
  else if (flexMeta) {
      var flexMetaContent = flexMeta.getAttribute("content");
      if (flexMetaContent) {

          var initial = flexMetaContent.match(/initial\-dpr=([\d\.]+)/),
              maximum = flexMetaContent.match(/maximum\-dpr=([\d\.]+)/);

          if (initial) {
              dpr = parseFloat(initial[1]);
              scale = parseFloat((1 / dpr).toFixed(2));
          }

          if (maximum) {
              dpr = parseFloat(maximum[1]);
              scale = parseFloat((1 / dpr).toFixed(2));
          }
      }
  }

  // viewport 或 flexible
  // meta 均未设置
  if (!dpr && !scale) {
      // QST
      // 这里的 第一句有什么用 ?
      // 和 Android 有毛关系 ?
      var u = (win.navigator.appVersion.match(/android/gi), win.navigator.appVersion.match(/iphone/gi)),
          _dpr = win.devicePixelRatio;

      // 所以这里似乎是将所有 Android 设备都设置为 1 了
      dpr = u ? ( (_dpr >= 3 && (!dpr || dpr >= 3))
              ? 3
              : (_dpr >= 2 && (!dpr || dpr >= 2))
              ? 2
              : 1
      )
          : 1;

      scale = 1 / dpr;
  }

  docElem.setAttribute("data-dpr", dpr);

  // 插入 viewport meta
  if (!vpMeta) {
      vpMeta = doc.createElement("meta");

      vpMeta.setAttribute("name", "viewport");
      vpMeta.setAttribute("content",
          "initial-scale=" + scale + ", maximum-scale=" + scale + ", minimum-scale=" + scale + ", user-scalable=no");

      if (docElem.firstElementChild) {
          docElem.firstElementChild.appendChild(vpMeta)
      } else {
          var div = doc.createElement("div");
          div.appendChild(vpMeta);
          doc.write(div.innerHTML);
      }
  }

  function setFontSize() {
      var winWidth = docElem.getBoundingClientRect().width;

      if (winWidth / dpr > 540) {
          (winWidth = 540 * dpr);
      }

      // 根节点 fontSize 根据宽度决定
      var baseSize = winWidth / 10;

      docElem.style.fontSize = baseSize + "px";
      flexible.rem = win.rem = baseSize;
  }

  // 调整窗口时重置
  win.addEventListener("resize", function() {
      clearTimeout(timer);
      timer = setTimeout(setFontSize, 300);
  }, false);


  // 自己加的
  // orientationchange 时也需要重算下吧
  win.addEventListener("orientationchange", function() {
      clearTimeout(timer);
      timer = setTimeout(setFontSize, 300);
  }, false);




  // pageshow
  // keyword: 倒退 缓存相关
  win.addEventListener("pageshow", function(e) {
      if (e.persisted) {
          clearTimeout(timer);
          timer = setTimeout(setFontSize, 300);
      }
  }, false);

  // 设置基准字体
  if ("complete" === doc.readyState) {
      doc.body.style.fontSize = 12 * dpr + "px";
  } else {
      doc.addEventListener("DOMContentLoaded", function() {
          doc.body.style.fontSize = 12 * dpr + "px";
      }, false);
  }

  setFontSize();

  flexible.dpr = win.dpr = dpr;

  flexible.refreshRem = setFontSize;

  flexible.rem2px = function(d) {
      var c = parseFloat(d) * this.rem;
      if ("string" == typeof d && d.match(/rem$/)) {
          c += "px";
      }
      return c;
  };

  flexible.px2rem = function(d) {
      var c = parseFloat(d) / this.rem;

      if ("string" == typeof d && d.match(/px$/)) {
          c += "rem";
      }
      return c;
  }
}(window, window.lib || (window.lib = {}));

